Algorithm 3: FIS using hybrid strategy.

Input: Number of feature fields: m; Threshold: $\epsilon$; Dictionary of orders: $\mathbb{D}$. Output: Hard vector of gated unit: $\mathbb{H}$. $\mathbb{W}\leftarrow$ Randomly initialize weights of features; $\mathbb{S}\leftarrow$ Compute Gumbel-softmax of $\mathbb{W}$; $k\leftarrow$ Get order of unit u from $\mathbb{D}$;; $inde{x}^{\left(k\right)}\leftarrow$ indexes of the top-k probabilities in $\mathbb{S}$; for i in $inde{x}^{\left(k\right)}$do